This application claims the priority of German application 196 28 762.6 filed in Germany on Jul. 17, 1996, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a cooling circuit of an internal combustion engine with a cast cylinder block with a coolant jacket, a cylinder head with coolant ducts, a common flange surface between the cylinder head and the cylinder block, as well as coolant passages inside the cylinder block that are designed as supply or return ducts, of which at least one coolant passage terminates in the flange area.
German Patent Document DE-43 22 030 A1 describes an internal combustion engine of the type referred to above in whose cooling circuit the coolant jacket of a cylinder block and the coolant ducts of a cylinder head are connected by coolant passages with a coolant pump. The coolant passages are located inside the cylinder block of the engine and designed as feed or return ducts. The coolant passages are partially in the form of bores in the cylinder block that terminate in a main duct of the coolant passage. These bores serve to supply the coolant ducts in the cylinder head. The problem with such a cooling circuit is the connection of the coolant jacket in the cylinder block to the main ducts by the bores. Since the main ducts are produced as part of the coolant passages in the cylinder block and are produced by casting, relatively large tolerances in terms of their position result, caused by changes in position between individual parts of the casting tool during the casting process. As a result of the differences in position of the cast parts of the coolant passage that fall within a range of tolerance governed by manufacturing, precise location of the bore with respect to the corresponding terminating area inside the coolant passage does not always result. Hence, sufficient processing reliability for mass production is not always achieved. Moreover the production of bores inside a cast cylinder block represents an additional time- and cost-intensive expense.
In addition, a cylinder block is known from U.S. Pat. No. 4,530,315 in which two rows of cylinders are arranged in the shape of a V. The coolant feed to the coolant jackets inside the cylinder blocks is performed by a lengthwise duct integrated into the base of the V formed by the cylinders. The connection of the lengthwise ducts of the cylinder blocks is made directly through relatively wide cast depressions.
On the other hand the invention is based on an object of improving a cooling circuit for such an internal combustion engine in such fashion that the connection between the coolant jacket inside the cylinder block and the coolant passages can be produced simply and reliably and is suitable for mass production. Areas that are especially important as far as flow technology is concerned (throttle points and transitions) should be possible to manufacture with a high level of precision as far as their position and assignment to individual parts of the cooling circuit are concerned. In addition, an adjustment of the through-flow volumes within the cooling circuit that is as simple as possible should be feasible.
This object is achieved according to the invention by providing an arrangement wherein a connection between the coolant jacket and at least one of the coolant passages is provided in the form of a slot starting at the flange area, which is cast into the cylinder block.
A connection of the coolant jacket inside the cylinder block, which is simple to manufacture and is reliable, with the sections of the coolant passages that are designed as supply or return ducts is obtained when this connection is in the form of a slot that starts in the flange area and is cast into the cylinder block. This slot, because of the fact that it is manufactured by casting, is precisely located and positioned and thus reliably produced by a suitable design of the casting tool. Deviations in the position of the cast coolant passage have no effect because of the tool-related direct shaping of the connection. In addition, a further workstep is avoided by using casting technology to make the connection, said step otherwise being necessary to produce a bore. In addition, in an especially advantageous manner, in the connection between the coolant jacket and the coolant passage that is produced by casting, adjustment of the coolant flow can be accomplished by the adapted geometry of the cast slot.
A high degree of accuracy in adjusting the coolant flow is achieved in an advantageous fashion if the depth of the slot connecting the coolant jacket and the coolant passage is greater than its width. Following the manufacture of the cast blank of the cylinder block, in a subsequent workstep the flange surface is machined with material removal. Because of the tolerances that result from manufacturing, the thickness of the amount to be removed from the flange surfaces differs from one part to the next. If during the production of the connecting slot its depth is made greater than its width, even with different removal rates, the influence on the cross sectional surface of the slot that is perpendicular to the flange surface is less than with a relatively wide design for the slot. The influence of the final machining of the cast blank on the cross sectional surface of the slot is minimized when the width B of the slot is reduced sufficiently to permit consistent manufacturing. In order to achieve a specific cross sectional area, therefore, the depth T of the slot is relatively great so that the influence of the removal rate in the final machining of the flange area is minimized.
The design of the cooling circuit and the production of the cylinder block of the internal combustion engine become especially simple and economical if the coolant jacket is connected both on the input and output sides in each case by at least one slot with the coolant passage (supply duct and return duct).
Uniform flow around the cylinder is achieved in an especially advantageous manner if the slot connected with the coolant jacket runs approximately radially with respect to the adjoining cylinder.
The flow through the coolant jacket is also made even more uniform if an input and an output slot are provided for each cylinder. Then in an especially simple fashion a transverse cooling flow can be formed within the cylinder block. This transverse cooling flow is very uniform if the slots on the input side and the output side are located diametrally opposite one another.
Especially in multicylinder internal combustion engines, in a particularly advantageous manner, an adjustment of the coolant flow can be accomplished if the slots connecting the coolant jacket and the coolant passages are adjusted geometrically so that their cross sections and therefore their depths in particular are dimensioned as a function of the pressure drop (distance from the coolant pump). By adjusting the geometry of all the slots, a uniform coolant stream can be obtained for each individual cylinder.
A coolant passage of this kind with cast slots for joining the coolant jacket and the coolant passages within the cylinder block is especially advantageously suitable for cylinder blocks made using the open-deck design.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.